Standardization of catheter-based treatment for atrial fibrillation

ABSTRACT

A method for treating atrial fibrillation in an atrium of a heart includes (a) acquiring an image or map of the atrium; (b) displaying the image or map of the atrium; (c) marking at least one feature on the image or map; (d) calculating dimensions of the at least one feature; (e) identifying one or more points on or within the atrium for treatment as part of a treatment plan; (f) determining paths to the one or more points on or within the atrium for treatment; (g) simulating insertion of a sheath into the atrium; (h) simulating insertion of a medical device through the sheath and into the atrium; (i) verifying that the one or more points on or within the atrium can be accessed for treatment; (j) computing an overall surface area of the atrium; (k) calculating an estimated area not treated in the atrium based on the treatment plan; (l) assessing whether macro-reentrant circuits can exist in the estimated area not treated in the atrium; (m) repeating steps (e)-(l) in the event step (l) indicates that macro-reentrant circuits can exist in the estimated area not treated in the atrium; and (n) implementing the treatment plan.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates, in general, to the planning andimplementing of medical procedures, and, in particular, to a new anduseful method for planning, simulating and conducting a medicalprocedure such as a cardiac treatment procedure as well as a new anduseful systematic method for treating atrial fibrillation underultrasound guidance and a new and useful method for planning, simulatingand conducting a medical procedure for preventing macro-reentrantcircuits from occurring in the atrium of the heart.

As is well known in the medical field, atrial fibrillation is a majordisease state and is characterized as a common sustained cardiacarrhythmia and is widely known to be a major cause of stroke. Thiscondition is perpetuated by reentrant wavelets, such as macro-reentrantcircuits, propagating in an abnormal atrial-tissue substrate withconduction heterogeneity and altered refractory period. Variousapproaches have been developed to interrupt these macro-reentrantcircuits wavelets, including surgical or catheter-mediated atriotomy.

A common approach for treating atrial fibrillation is through the use ofradio-frequency (RF) ablation energy using an ablation catheter. Inusing an RF ablation catheter, continuous linear lesions are formed byablation in order to segment the heart tissue of the atrium. Bysegmenting the heart tissue, no electrical activity can be transmittedfrom one segment to another. Preferably, the segments are made verysmall in order to be able to sustain the fibrillatory process.

As a result, several catheter ablation techniques may be used to treatatrial fibrillation by ablating lines in the left atrium. The relevantanatomical features involved in this type of procedure are schematicallyillustrated in FIG. 1B. Typically, for this purpose, the physicianattempts to ablate lines in the left atrium 10 around the ostia of thepulmonary veins (13, 14, 16 and 18), in order to isolate foci of thearrhythmia. The physician may also ablate lines along the mitral isthmusconnecting the right inferior pulmonary vein to the mitral valve 20and/or the left atrial appendage ridge between the left superiorpulmonary vein and the left atrial appendage 22.

And, as can be greatly appreciated, ablation of structures in the leftatrium can be a-very complex and even tricky procedure and is heavilydependent upon the individual skill of the operating physician. Part ofthe procedure complexity includes accessing the left atrium 10 in anefficient and safe manner. Thus, in order to properly reach or accessthe left atrium 10, the physician must pass a sheath 40 through the venacava into the right atrium, and then through the interatrial septum 11at fossa ovalis 12 and into the left atrium 10. The physician then mustpass an ablation catheter 50 through the sheath 40 into the left atrium10, and must then position the catheter 50 at a succession of locationsthat define the ablation lines. The procedure is shown schematically inFIG. 1B. Optimal deployment of the sheath 40 and catheter 50 for thesepurposes varies substantially from patient to patient, due to a highlevel of anatomical variability. Failure to position and operate themedical devices or procedure tools correctly may result, at the least,in failure to fully isolate a focus of the arrhythmia, and can causefatal complications. As a result, left atrial ablation has a sub optimalsuccess rate.

SUMMARY OF THE INVENTION

The present invention is directed to several novel inventions to includemethods for planning and implementing medical procedures. In particular,one novel method in accordance with the present invention is directed toa new and useful method for planning, simulating and conducting amedical procedure such as a cardiac treatment procedure. Another novelmethod in accordance with the present invention is directed to a new anduseful systematic method for treating atrial fibrillation underultrasound guidance. Additionally, another novel method in accordancewith the present invention is directed to a new and useful systematicmethod for planning, simulating and conducting an atrial fibrillationprocedure under ultrasound guidance. A further novel method inaccordance with the present invention is directed to, a new and usefulmethod for planning, simulating and conducting a medical procedure forpreventing macro-reentrant circuits from occurring in the atrium of theheart.

In accordance with one invention of the present invention, a method forpre-planning a cardiac procedure on a heart comprises the steps of:

acquiring an image or map of the heart;

displaying the image or map of the heart;

marking at least one feature on the image or map;

calculating dimensions of the at least one feature;

identifying one or more points on or within the heart for treatment;

determining paths to the one or more points on or within the heart fortreatment;

simulating insertion of a sheath into the heart;

simulating insertion of a medical device through the sheath and withinthe heart; and

verifying that the one or more points on or within the heart can beaccessed for treatment.

In accordance with another embodiment of the present invention, a methodfor developing a plan for a cardiac procedure comprises the steps of:

acquiring an image or map of the heart;

displaying the image or map of the heart;

marking at least one feature on the image or map;

calculating dimensions of the at least one feature;

identifying one or more points on or within the heart for treatment;

determining paths to the one or more points on or within the heart fortreatment;

simulating insertion of a sheath into the heart;

simulating insertion of a medical device through the sheath and withinthe heart; and

verifying that the one or more points on or within the heart can beaccessed for treatment.

Another embodiment in accordance with the present invention is a methodfor pre-planning and performing a cardiac procedure on a heartcomprising the steps of:

acquiring an image or map of the heart;

displaying the image or map of the heart;

marking at least one feature on the image or map;

calculating dimensions of the at least one feature;

identifying one or more points on or within the heart for treatment;

determining paths to the one or more points on or within the heart fortreatment;

simulating insertion of a sheath into the heart;

simulating insertion of a medical device through the sheath and withinthe heart;

verifying that the one or more points on or within the heart can beaccessed for treatment; and

performing a medical procedure on or within the heart.

A further embodiment according to the present invention is a method fordeveloping a plan and performing a cardiac procedure on a heartcomprising the steps of:

acquiring an image or map of the heart;

displaying the image or map of the heart;

marking at least one feature on the image or map;

calculating dimensions of the at least one feature;

identifying one or more points on or within the heart for treatment;

determining paths to the one or more points on or within the heart fortreatment;

simulating insertion of a sheath into the heart;

simulating insertion of a medical device through the sheath and withinthe heart;

verifying that the one or more points on or within the heart can beaccessed for treatment; and

performing a medical procedure on or within the heart.

Additionally, another embodiment of the present invention is a methodfor simulating a cardiac procedure on a heart comprising the steps of:

acquiring an image or map of the heart;

displaying the image or map of the heart;

marking at least one feature on the image or map;

calculating dimensions of the at least one feature;

identifying one or more points on or within the heart for treatment;

determining paths to the one or more points on or within the heart fortreatment;

simulating insertion of a sheath into the heart;

simulating insertion of a medical device through the sheath and withinthe heart; and

verifying that the one or more points on or within the heart can beaccessed for treatment.

Also, another embodiment according to the present invention is a methodfor simulating and developing a plan for a cardiac procedure comprisingthe steps of:

acquiring an image or map of the heart;

displaying the image or map of the heart;

marking at least one feature on the image or map;

calculating dimensions of the at least one feature;

identifying one or more points on or within the heart for treatment;

determining paths to the one or more points on or within the heart fortreatment;

simulating insertion of a sheath into the heart;

simulating insertion of a medical device through the sheath and withinthe heart; and

verifying that the one or more points on or within the heart can beaccessed for treatment.

Moreover, another embodiment of the present invention is directed to amethod for simulating and performing a cardiac procedure on a heartcomprising the steps of:

acquiring an image or map of the heart;

displaying the image or map of the heart;

marking at least one feature on the image or map;

calculating dimensions of the at least one feature;

identifying one or more points on or within the heart for treatment;

determining paths to the one or more points on or within the heart fortreatment;

simulating insertion of a sheath into the heart;

simulating insertion of a medical device through the sheath and withinthe heart;

verifying that the one or more points on or within the heart can beaccessed for treatment; and

performing a medical procedure on or within the heart.

Furthermore, another embodiment of the present invention is a method forsimulating a cardiac procedure, developing a plan and performing acardiac procedure on a heart comprising the steps of:

acquiring an image or map of the heart;

displaying the image or map of the heart;

marking at least one feature on the image or map;

calculating dimensions of the at least one feature;

identifying one or more points on or within the heart for treatment;

determining paths to the one or more points on or within the heart fortreatment;

simulating insertion of a sheath into the heart;

simulating insertion of a medical device through the sheath and withinthe heart;

verifying that the one or more points on or within the heart can beaccessed for treatment; and

performing a medical procedure on or within the heart.

Another invention according to the present invention is directed to amethod for treating atrial fibrillation in a heart of a patient,comprising the steps of:

placing an ultrasonic catheter in a first chamber of the heart;

acquiring three-dimensional ultrasonic image slices of a second chamberof the heart and at least a portion of surrounding structures of thesecond chamber using the ultrasonic catheter placed in the firstchamber;

reconstructing a three-dimensional ultrasonic image reconstruction basedon the three-dimensional ultrasonic image slices;

displaying the three-dimensional ultrasonic image reconstruction;

identifying at least one key landmark on the three-dimensionalultrasonic image reconstruction;

marking the least one key landmark on the three-dimensional ultrasonicimage reconstruction;

penetrating the septum for accessing the second chamber of the heartwhile using the marked at least one key landmark for guidance;

positioning a sheath through the penetrated septum and within the secondchamber of the heart;

inserting an ablation catheter through the sheath and into the secondchamber of the heart; and

ablating a portion of the second chamber of the heart using the ablationcatheter while under observation with the ultrasound catheter located inthe first chamber of the heart.

Additionally, another embodiment of the invention is a method forsimulating, developing a plan and treating atrial fibrillation in aheart of a patient, comprising the steps of:

placing an ultrasonic catheter in a first chamber of the heart;

acquiring three-dimensional ultrasonic image slices of a second chamberof the heart and at least a portion of surrounding structures of thesecond chamber using the ultrasonic catheter placed in the firstchamber;

reconstructing a three-dimensional ultrasonic image reconstruction basedon the three-dimensional ultrasonic image slices;

displaying the three-dimensional ultrasonic image reconstruction;

identifying at least one key landmark on the three-dimensionalultrasonic image reconstruction;

marking the least one key landmark on the three-dimensional ultrasonicimage reconstruction;

identifying one or more points for treatment on the three-dimensionalultrasonic image reconstruction;

determining paths to the one or more points for treatment using themarked at least one key landmark as a guide;

simulating on the three-dimensional ultrasonic image reconstructioninsertion of a sheath into the heart;

simulating on the three-dimensional ultrasonic image reconstructioninsertion of a medical device through the sheath and within the secondchamber of the heart;

verifying that the one or more points for treatment in the secondchamber of the heart can be accessed for treatment;

outlining a plan based on the simulation;

using the plan, penetrating the septum of the heart for accessing thesecond chamber of the heart;

positioning a sheath through the penetrated septum and within the secondchamber of the heart;

inserting an ablation catheter through the sheath and into the secondchamber of the heart; and

ablating a portion of the second chamber of the heart using the ablationcatheter while under observation with the ultrasound catheter located inthe first chamber of the heart.

Furthermore, the present invention is also directed to a method forpreventing macro-reentrant circuits from occurring in a portion of aheart of a patient, comprising the steps of:

(a) acquiring an image or map of the portion of the heart;

(b) displaying the image or map of the portion of the heart;

(c) marking at least one feature on the image or map;

(d) calculating dimensions of the at least one feature;

(e) identifying one or more points on or within the heart for treatmentas part of a treatment plan;

(f) determining paths to the one or more points on or within the heartfor treatment;

(g) simulating insertion of a sheath into the heart;

(h) simulating insertion of a medical device through the sheath andwithin the heart;

(i) verifying that the one or more points on or within the heart can beaccessed for treatment;

(j) computing an overall surface area of the portion of the heart;

(k) calculating an estimated area not treated in the portion of theheart based on the treatment plan;

(l) assessing whether macro-reentrant circuits can exist in theestimated area not treated in the portion of the heart;

(m) repeating steps (e)-(l) in the event step (l) indicates thatmacro-reentrant circuits can exist in the estimated area not treated inthe portion of the heart; and

(n) implementing the treatment plan.

Another embodiment of this invention in accordance with the presentinvention is a method for treating atrial fibrillation in an atrium of aheart of a patient, comprising the steps of:

(a) acquiring an image or map of the atrium;

(b) displaying the image or map of the atrium;

(c) marking at least one feature on the image or map;

(d) calculating dimensions of the at least one feature;

(e) identifying one or more points on or within the atrium for treatmentas part of a treatment plan;

(f) determining paths to the one or more points on or within the atriumfor treatment;

(g) simulating insertion of a sheath into the atrium;

(h) simulating insertion of a medical device through the sheath and intothe atrium;

(i) verifying that the one or more points on or within the atrium can beaccessed for treatment;

(j) computing an overall surface area of the atrium;

(k) calculating an estimated area not treated in the atrium based on thetreatment plan;

(l) assessing whether macro-reentrant circuits can exist in theestimated area not treated in the atrium;

(m) repeating steps (e)-(l) in the event step (l) indicates thatmacro-reentrant circuits can exist in the estimated area not treated inthe atrium; and

(n) implementing the treatment plan.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. The invention itself, however, both as toorganization and methods of operation, together with further objects andadvantages thereof, may be understood by reference to the followingdescription, taken in conjunction with the accompanying drawings inwhich:

FIG. 1A is a flow chart illustrating a method for simulating, planningand implementing a medical procedure in accordance with one embodimentof the present invention;

FIG. 1B is a schematic illustration of the method of FIG. 1A on adisplay for simulating, planning and implementing a cardiac procedure inthe left atrium in accordance with the present invention;

FIG. 2A is a flow chart illustrating a method for conducting a cardiacprocedure using ultrasound guidance in accordance with a secondembodiment of the present invention;

FIG. 2B is a flow chart illustrating a method for simulating, planningand conducting a cardiac procedure using ultrasound guidance inaccordance with a third embodiment of the present invention;

FIG. 2C is a schematic illustration of the methods of FIGS. 2A and 2B ona display for simulating, planning and implementing a cardiac procedureusing ultrasound guidance in accordance with the present invention;

FIG. 3A is a flow chart illustrating a method for simulating, planningand conducting a cardiac procedure in order to prevent macro-reentrantcircuits in accordance with a fourth embodiment of the presentinvention; and

FIG. 3B is a schematic illustration of the method of FIG. 3A on adisplay for simulating, planning and implementing a cardiac procedurewhile preventing macro-reentrant circuits in accordance with the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to several novel methods for planning andimplementing medical procedures. In particular, one novel method inaccordance with the present invention is directed to a new and usefulmethod for planning, simulating and conducting a medical procedure suchas a cardiac treatment procedure. Another novel method in accordancewith the present invention is directed to a new and useful systematicmethod for treating atrial fibrillation under ultrasound guidance. Yetanother novel method in accordance with the present invention isdirected to a new and useful systematic method for planning, simulatingand conducting an atrial fibrillation procedure under ultrasoundguidance. A further novel method in accordance with the presentinvention is directed to a new and useful method for planning,simulating and conducting a medical procedure for preventingmacro-reentrant circuits from occurring in the atrium of the heart.

FIGS. 1A and 1B illustrate a novel method, generally designated 100, inaccordance with the present invention for planning simulating andconducting a medical procedure such as a cardiac treatment procedure.The method 100 in accordance with the present invention comprises step105 of obtaining, acquiring or using images and/or maps or pre-acquiredimages and/or maps of the left atrium 10 (FIG. 1B) in computersimulation of the process of left atrial ablation displayed on display8. The image or map may include, for example, a three-dimensional (3D)ultrasound image, MRI image, CT image or the like or an electrical mapor electroanatomical map such as provided by the CARTO™ mapping andnavigation system (manufactured and sold by Biosense Webster, Inc. ofDiamond Bar, Calif.), i.e. a CARTO™ map (which may be pre-registeredwith the image). The simulation and method 100 in accordance with thepresent invention can be used both in order to plan the medicalprocedure and to guide the physician in the course of carrying out theprocedure. An exemplary scenario is described below.

Planning the Ablation Procedure

As best illustrated in FIG. 1A, in step 105, the physician acquires animage and/or map of the heart and marks key features 110 of the leftatrium 10 (all shown in FIG. 1B), including the fossa ovalis (or foramenovale) 12, ostia of the four pulmonary veins (right superior pulmonaryvein “RSPV” 13, right inferior pulmonary vein “RIPV” 14, left superiorpulmonary vein “LSPV” 16, and left inferior pulmonary vein “LIPV” 18),annulus of the mitral valve 20, and ostia of the left atrial appendage22. Alternatively, computerized image recognition algorithms mayidentify some or all of these features. In step 115, the dimensions ofthese features or key features of left atrium 10 are measured orcalculated. One dimension of these features that are calculated is thediameter for each key feature. In this example, the diameters of thefeatures are calculated 115 and the next step 120 is to determinedesired paths for treatment based on the calculated dimensions (in thisexample, diameters of the features). Accordingly, for an RF ablationprocedure and treatment with an ablation catheter 50, the diameters ofthe key features are calculated for use in determining the paths of theablation lines to be created by the ablation catheter 50.

Based on the image/map and anatomical landmarks (key features)identified in steps 110 and 115, pathways for treatment are determined120 and a computer simulates the process of inserting the sheath 40(step 125) from the vena cava, through the right atrium and interatrialseptum 11 through fossa ovalis/foramen ovale 12, into the left atrium 10as shown in FIG. 1B. This step 125 allows the angle of attack andpenetration depth of the sheath 40 to be determined in advance, in orderto avoid injury to the patient during actual penetration of the septum11.

The computer used for all embodiments of the present invention set forthin this disclosure comprises signal processing circuits with softwareand algorithms and is graphically represented in FIGS. 1B, 2C and 3B asdisplay 8. Display 8 is also used to depict images and/or maps as wellas the simulations and planning steps to include graphic representationsof medical devices such as sheaths 40, ablation catheters 50, ultrasoundimaging catheters 55, etc.

In step 130, the computer is used to simulate insertion of selectedablation catheters 50 through the sheath 40. Typically, a range ofdifferent catheters 50 are available wherein each catheter 50 ischaracterized by a certain radius of curvature as best shown in FIG. 1B.As illustrated in FIG. 1B, a catheter 50 of a certain curvature, afterinsertion through the sheath 50, is shown in two different orientationson display 8, which are separated by approximately 180° of rotation. Thecomputer is then used to simulate the operation of a number of differentdegrees of freedom in order to ascertain the ability of the catheter 50to reach all the of desired points that must be ablated in the leftatrium (one or more points targeted for treatment such as ablation).

Additionally, computer simulation is also used for determining possibletrajectories of the catheter 50 against the atrial wall of left atrium10, depending on the depth of insertion and the orientation angle of thecatheter 50 into the left atrium 10, along with the mechanicalproperties and mechanical effect of the atrial wall (with which thecatheter 50 is in contact) on a particular trajectory of the catheter50. Moreover, computer simulation is also used to determine the effectof the depth of extension of the sheath 40 into the left atrium 10 mayhave on the catheter trajectory. Steps 130 and 135 can be performed fordifferent catheters 50 having different radii of curvature.

At the discretion of the physician, these steps are used to choose anoptimal catheter 50 and to conduct step 135 which is to verify that thecatheter 50 will be able to access all points in the left atrium thatare to be ablated (one or more points in the left atrium to be treated).As best illustrated in FIG. 1B, indicia 60, such as symbols, labels,annotations or check marks, are identified directly on display 8. Inthis example, check marks are used as indicia 60 at the graphicrepresentations of RSPV 13, LSPV 16 and LIPV 18 on display 8, indicatingthat the selected catheter 50 will be able to trace and form ablationlines around these features, while indicia 60 in the form of a questionmark symbol is shown on the RIPV 14 graphic representation on display 8as a feature that may be inaccessible using the selected catheter 50.

Based on the selected catheter 50 and on the features and theirdimensions of the cardiac anatomy, the physician and/or computer(physician with or without the aid of computer and simulation softwareand algorithm) designs the ablation plan 140 for this patient by markingthe one or more points to be treated such as through tracing the linesin the left atrium 10 that are to be ablated. The computer thencalculates the execution parameters, such as the RF power, electrodetype and burn duration, that are required to achieve complete transmuralablation without danger of puncturing the heart wall or causingcollateral damage to extracardiac structures like the esophagus. Theseparameters may be based on the tissue thickness, as given by the 3Dimage of the heart.

Execution of the Procedure

The computer is programmed to give the physician instructions in thecourse of the procedure, based on the ablation plan 140 and executionparameters as previously determined (outlined above). The treatment(ablation) plan is then implemented 145. And, in step 150, the computermonitors execution of the procedure by tracking the position of thecatheter 50 (and the sheath 50 if so desired), using suitable positionsensors such as the electromagnetic position sensors used in the CARTO™mapping and navigation system (not shown). Accordingly, in step 150, thecomputer can instruct the physician as to where and when to start andstop ablating, as well as where and at what angle to push the sheath 40through the septum 11. In step 150, the computer can also provide realtime guidance to the physician in step 145 (conducting and implementingthe ablation plan) by guiding and cautioning the physician, i.e. providea warning to the physician, as to possible dangerous conditions anddeviations from the ablation plan 140.

The method according to the present invention is shown in FIGS. 1A and1B, is particularly useful for acquiring an anatomical model (of theheart, particularly the left atrium 10); simulating an invasiveprocedure based on the anatomical model and on known properties of aninstrument (or instruments) that is to be used in the procedure; andtracking the position of the instrument using a position sensor, inorder to guide the actual procedure based on the simulated procedureoutlined above.

This method in accordance with the present invention is particularlyadvantageous in that it permits accurate pre-planning of complexprocedures, in order to find an optimal choice of tools (medical devicesor medical instruments) and maneuvers, i.e. use thereof, that areexpected to give a successful result, followed by monitoring, guidanceand validation of the actual procedure to ensure that the resultcomplies with the simulation.

Additionally, the method described above may also be used under roboticcontrol; for instance, in a closed-loop control manner using roboticallycontrolled and commanded instruments for catheter navigation andablation.

Although this method of according to the present invention isparticularly suited for treatment of atrial fibrillation by ablation ofthe left atrium 10, the principles of the invention may be applied forthe treatment of ventricular tachycardia by ablating around a scar inthe left ventricular wall, or for cell-based or gene-based therapies byinjection catheter, as well as in all other medical applications such asinvasive procedures in the fields of orthopedics, urology, neurology,thoracic, gastrointestinal, vascular, etc.

The present invention is also directed to a novel systematic method forcarrying out ablation treatment of atrial fibrillation in the leftatrium as best illustrated in FIGS. 2A, 2B and 2C. This method inaccordance with present invention is conducted under ultrasound guidanceusing an ultrasound catheter 55 (FIG. 2C) placed in the right atrium 30of the patient's heart. Ultrasound catheter 55 can include a positionsensor, such as an electromagnetic position sensor as disclosed in U.S.patent application Ser. No. 11/114,847 filed Apr. 26, 2005, which isincorporated by reference herein. Thus, in this embodiment, theultrasound catheter 55 with position sensor is used in conjunction witha location system having a computer and signal processing circuits fordetermining the accurate location of the position sensor and catheter 55and navigating the catheter 55 in the patient's body.

In this exemplary embodiment, the steps of the procedure 90 a areschematically, illustrated in FIG. 2A and outlined below. First, in step106. the physician places ultrasound catheter 55 in one chamber of thepatient's heart and obtains one or more images of an adjacent chamberusing the ultrasound catheter 55. For example, the physician insertsultrasound catheter 55 into the right atrium 30 (FIG. 2C) and aims theultrasound beam 57 projected from catheter 55 at an adjacent chamber,for instance, the left atrium 10 and uses the catheter 55 to acquireultrasound images (two-dimensional “2D” ultrasound images) of the leftatrium 10 and surrounding structures. The position sensor (not shown)used on the ultrasound catheter 55 and its associated location system(not shown) allow for accurate location determination (determination ofposition coordinates and orientation coordinates) of the position sensorand catheter 55. For example, the position sensor allows for a portionof catheter 55 to be accurately tracked and navigated using threedimensions of position coordinates (X, Y and Z coordinate axisdirections) and at least two dimensions of orientation coordinates (yawand pitch) to include up to three dimensions of orientation coordinates(yaw, pitch and roll). Accordingly, since the location coordinates(position coordinates and orientation coordinates) for a portion of thecatheter 55 are determined using a location system (not shown)operatively connected to the position sensor of the catheter 55,three-dimensional ultrasound slices are obtained using the 2D ultrasoundimages and their associated location coordinates for each pixel of eachrespective 2D ultrasound image.

Thus, the computer uses the location coordinates (position coordinatesand orientation coordinates) for each pixel of each 2D ultrasound imageand makes a resulting three-dimensional ultrasound image slice. Then, instep 108, the three-dimensional ultrasound image slices acquired by thecatheter 55 and generated by the computer are also used by the computer(having reconstruction algorithms and reconstruction software) toreconstruct a 3D ultrasound image reconstruction (3D model or 3Dreconstructed image) of the left atrium 10. In addition, thereconstructed 3D ultrasound image model or reconstruction will includethe aortic valve 26 and the ascending aorta 24, located behind the leftatrium 10.

In the next step 110, key features such as landmarks are identified onthe 3D reconstructed image, either automatically or interactively, bythe physician. These landmarks include the planes and outlines of thefossa ovalis (or foramen ovale), 12 and the aortic valve 26, as well asthe aorta itself 24. Other key landmarks typically include the ostia ofthe four pulmonary veins (right superior pulmonary vein “RSPV” 13, rightinferior pulmonary vein “RIPV” 14, left superior pulmonary vein “LSPV”16, and left inferior pulmonary vein “LIPV” 18), annulus of the mitralvalve 20, and ostia of the left atrial appendage 22.

In preparation for inserting the ablation catheter 50 from the rightatrium 30 into the left atrium 10, in step 146 (FIG. 2A) the physicianpierces the septum 11 at the fossa ovalis 12 using a needle or thesheath 40 as shown in FIG. 2C. The locations of the aortic valve 26 andaorta 24 in the 3D ultrasound image are indicated to ensure that thephysician does not accidentally pierce the aorta 24 with the needle. Thesystem and computer can be programmed to automatically guide thephysician as to the correct direction and depth for insertion of theneedle through the septum 11. The ultrasound catheter 55 may be used inDoppler mode to observe creation of the hole in the septum 11 bydetecting the flow of blood through the hole from the left atrium 10 tothe right atrium 30.

In step 147, the ablation catheter 50 (and any other desired medicaldevices if needed for the procedure) is inserted (through the sheath 40)into the left atrium 10 in order to create the desired ablation pattern.In step 148, the ultrasound catheter 50 remains positioned only in theright atrium 30 and is used to image 57 the area of the tip of theablation catheter 50 (located in the left atrium 10) in order to observeand image the results of ablation in real time. The ultrasound catheter55 or/and the ablation catheter 50 may be automatically controlled, forinstance under robotic control, so that the 2D ultrasound fan orprojection 57 tracks the location of the ablation catheter 50 as theablation catheter 50 moves within the left atrium 10. After completionof the treatment step, i.e. ablation step (under ultrasound guidance) instep 148, the ultrasound catheter 55 captures further ultrasound imagesof the left atrium 10 for the purpose of lesion assessment and to ensurethat blood flow through the pulmonary veins 13, 14, 16 and 18 has notbeen compromised in step 152. Thus, step 152 is used to assess the levelof treatment provided and to verify proper blood flow through thechambers of the heart and key vessels such as the pulmonary veins 13,14, 16 and 18.

This method according to the present invention is particularlyadvantageous in that it enhances the precision and safety of ablationtreatment for left atrial fibrillation, by means of a novel combinationof intracardiac ultrasound imaging, position sensing, preplanning,simulation and guidance (discussed in greater detail below).

Another embodiment of this method 90 b in accordance with the presentinvention is illustrated in FIG. 2B and uses many of the steps outlinedfor the method 90 a (FIG. 2A), and likewise the same reference numeralsare used for the same method steps. However, an additional step,generally designated 112, is the pre-planning and simulation step, whichare the same steps: calculating dimensions of features 115, determiningpaths for treatment 120, simulation the sheath insertion process 125,simulation of devices inserted through the sheath 130, verifying accessto all points to be treated 135, designing the treatment plan 140, andmonitoring procedure and providing guidelines 150 illustrated in FIG. 1Aand outlined in detail previously above.

Additionally, these methods described above and illustrated in FIGS. 2Aand 2B may also be used under robotic control, for instance, in aclosed-loop control manner using robotically controlled and commandedinstruments for catheter navigation and ablation.

Although the methods of the present invention illustrated in FIGS. 2Aand 2B are particularly suited for treatment of atrial fibrillation byablation of the left atrium, the principles of the invention may beapplied in the ventricles and in other sorts of invasive proceduresperformed on other body organs such as those briefly identifiedpreviously by way of example.

Another method in accordance with the present invention is directed totreating atrial fibrillation in the heart through a novel and efficientmethod for preventing macro-reentrant circuits from occurring the atrialwall of the heart. As is well known, catheter-based treatments ofleft-atrial fibrillation generally involve ablation of myocardial tissuein a pattern that is designed to encircle, and thus isolate, theorifices of the pulmonary veins. This pattern of treatment is based onwork (by known Electrophysiologist Dr. Haissaguerre and his colleagues)showing that atrial fibrillation is usually induced, by stimulation froma site within the orifice of one or more of the pulmonary veins.Treatment of this sort, however, has an unacceptably high failure ratewhen used as the sole treatment for atrial fibrillation that istypically around 30% failure rate.

It is postulated that the reason for this high failure rate is thatchronic atrial fibrillation does not require any sort of inductionstimulus. Rather, as shown by the work of known electrophysiologists Dr.Wijffels and Dr. Allessie, once the atria begin to fibrillate, theyundergo a process of electrical “remodeling,” which causes fibrillationto continue even in the absence of a specific induction site.

Accordingly, the method in accordance with the present invention isdirected to ablation treatment for treating atrial fibrillation that isnot only directed to isolating induction sites, such as the ostia of thepulmonary veins (right superior pulmonary vein “RSPV” 13, right inferiorpulmonary vein “RIPV” 14, left superior pulmonary vein “LSPV” 16, andleft inferior pulmonary vein “LIPV” 18 shown in FIG. 3B), but also toprevent macro-reentrant circuits 70 from occurring within the atrialwall itself in left atrium 10.

The physical size of these macro-reentrant circuits 70 is determined bythe duration of the refractory period at any given site in the atria.Normally, atrial refractory periods are long (average duration ofrefractory period under normal conditions in a time range of 120-150msec.), and the macro-reentrant circuits are consequently largetypically greater than 6-7 cm in diameter).

In atrial fibrillation, however, the refractory period may be muchshorter, i.e. in a time range from 80-100 msec., so that themacro-reentrant circuits 70 may be small enough to survive between theactual ablation lines 65, i.e. macro-reentrant circuits 70 as small as 1cm in diameter. The circular paths marked 70 between the ablationlesions 65 shown in FIG. 3B illustrate this situation. This problembecomes more difficult to manage the larger the volume of the atria andsurface area of the atrial endocardium.

In response to this problem, the present invention offers a novel method95 for preventing macro-reentrant circuits 70 (FIG. 3B) in the treatmentof atrial fibrillation as schematically shown in FIG. 3A. In accordancewith the method 95 of the present invention, the first step 140 is todesign a treatment plan, i.e. designing an ablation strategy (thatincludes both pulmonary vein isolation and the ablation lines requiredfor proper isolation and block) on the surface of the atrium 10 using apre-acquired 3D image (such as CT, MR and/or ultrasound) image. Again,the development of the treatment strategy (outlined in step 140) canalso include the general pre-planning and simulation step 112 of FIG. 1Asuch as one or more of individual steps to include step 105 acquiring animage and/or map of the surface or portion of the heart such as theatrium or portion of the atrium or other chamber or vessel; anddisplaying the image and/or map of the surface or portion of the heartor atrium on the display 8 (FIG. 3B); step 110 marking at least onefeature on the image and/or map (such as one or more key features toinclude anatomical landmarks); step 115 calculating dimensions of theone or more key features to include determining the diameter for each ofthe key features, and identifying one or more points on or within theheart for treatment as part of a treatment plan; step 120 determiningthe pathways for treatment; step 125 simulating insertion of the sheath40; step 130 simulating insertion of other medical devices, such asablation catheters, through the sheath and into the heart and atrium;step 135 verifying that the one or more points on or within the heartcan be accessed for treatment; and step 140 designing the treatment planwherein each of these steps can be used in any combination or sequence.Details of these steps have also been described previously above.

As schematically shown in FIG. 3A, after the treatment strategy has beendeveloped and outlined in the treatment plan step 140, the overallendocardial surface area of the atrium 10 is computed in step 160. Forpurposes of the present invention, step 160 is also directed tocomputing any portion of the endocardial surface area and not just theentire surface area of the endocardium surface, but rather any surfaceor portion of surface of interest. After computing the endocardialsurface of the atrium, the estimated area of each segment is calculatedfollowing the planned ablation pattern in step 165. Representativeexamples of segments are illustrated in FIG. 3B and are the areasbetween lines of ablation 65, i.e. non-ablated areas between ablationlines 65. Then, in step 170 each segment (non-ablated area or estimatedarea not treated as part of the designed treatment plan) is assessed todetermine whether or not it is possible for each segment to harbor orlikely to experience macro-reentrant circuits 70. Step 170 is conductedover a range of likely refractory periods such as the refractory periodranges outlined previously above (or set by the user—if known). If it islikely that one or more of the segments may still be large enough toharbor macro-reentrant circuits, then the therapeutic plan is amended ormodified (step 172) to reduce the areas of the segments, i.e. reduce thesegment size by planning for additional ablation lines or lines of blockdesignated by reference numeral 75 in FIG. 3B. And, step 170 isconducted again in order to determine if the reduced segment (segmentwith a smaller area or size now defined by additional lines of ablation75) is capable of harboring or experiencing macro-reentrant circuits 70.

In the event that the segment size is sufficient in size or are suchthat it is not capable of harboring or experiencing macro-reentrantcircuits 70, then the treatment plan is implemented and the therapy,such as ablation treatment, is provided by the physician in step 175.

Again, execution the therapeutic plan at step 175 can be conductedmanually (by the physician) or under robotic control. After executingthe treatment plan, the actual area of each segment is measured in step180. In step 180, the measurement of the actual area of each segmentcreated after ablation lines 65 have been made (including implementingthe planned lines of ablation 75 for a reduced segment size) is normallyconducted at the end of the procedure. However, in step 185, ifmeasurement of the actual segment size or actual segment area revealsthat it is still possible for macro-reentrant circuits to exist, thenthe therapeutic plan is amended or revised at step 172 in an effort toreduce the segment size in a manner that is incapable of experiencingmacro-reentrant circuits. And, the amended plan will be implemented atstep 175 with the remainder of steps 180 and 185 conducted again.

In the event that the measurement of the actual segment size or actualsegment area at step 180 reveals that it is not possible formacro-reentrant circuits to exist (analysis conducted at step 185), thenthe procedure is considered completed or finished (step 190 indicatingthat the procedure is complete).

As noted above, additional ablation lines 75 are added to the originalablation pattern 65 (either in the planning stage at step 170 and 172 orafter the first stage of execution at step 185 and 172) in order to cutsegments that may still be large enough to sustain macro-reentrantcircuits.

As is well known, the prior art and current surgical and catheter-basedtreatments for atrial fibrillation use approximately the same lesionpattern for all patients and, as a consequence, these procedures atpatients suffer from high failure rates. The present invention solvesthis problem by providing a systematic way to tailor the treatment tothe anatomical and electrophysiological characteristics of each specificpatient, based on quantitative measures taken from images and/or maps ofthe heart in question. Thus, it is believed that this novel approach,system and method will increase the success rate of atrial fibrillationtreatment.

In as much as the foregoing specification comprises preferredembodiments of the invention, it is understood that variations andmodifications may be made herein, in accordance with the inventiveprinciples disclosed, without departing from the scope of the invention.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes and substitutions will now occur to those skilled inthe art without departing from the invention. Accordingly, it isintended that the invention be limited only by the spirit and scope ofthe appended claims.

What is claimed is:
 1. A method for preventing macro-reentrant circuitsfrom occurring in a portion of a heart of a patient, comprising thesteps of: (a) acquiring an image or map of the portion of the heart; (b)displaying the image or map of the portion of the heart; (c) marking atleast one feature on the image or map; (d) calculating dimensions of theat least one feature; (e) identifying one or more points on or withinthe heart for treatment as part of a treatment plan; (f) determiningpaths to the one or more points on or within the heart for treatmentbased on the dimensions of the at least one marked feature; (g)simulating, on a computer, insertion of a sheath into the heart throughone of the paths; (h) simulating, on the computer, insertion of amedical device through the sheath and within the heart; (i) verifyingthat the one or more points on or within the heart can be accessed bythe medical device for treatment as part of the treatment plan; (j)computing an overall surface area of the portion of the heart; (k)calculating an estimated area not treated in the portion of the heartbased on the treatment plan and in accordance with the overall surfacearea of the portion of the heart; (l) assessing whether macro-reentrantcircuits can exist in the estimated area not treated in the portion ofthe heart; (m) repeating steps (e)-(l) in the event step (l) indicatesthat macro-reentrant circuits can exist in the estimated area nottreated in the portion of the heart; and (n) implementing the treatmentplan of steps (g) through (i).
 2. The method according to claim 1,further comprising measuring an actual area not treated in the portionof the heart after step (n).
 3. The method according to claim 2, furthercomprising assessing whether macro-reentrant circuits can exist in theactual area not treated in the portion of the heart.
 4. The methodaccording to claim 3, further comprising repeating steps (e)-(l) in theevent step (l) indicates that macro-reentrant circuits can exist in theactual area not treated in the portion of the heart.
 5. The methodaccording to claim 4, further comprising implementing a revisedtreatment plan in the event step (l) indicates that macro-reentrantcircuits can exist in the actual area not treated in the portion of theheart.
 6. The method according to claim 5, further comprising monitoringthe treatment and robotically guiding the medical device according tothe treatment plan.
 7. The method according to claim 5, furthercomprising using ablation as the treatment.
 8. The method according toclaim 7, further comprising conducting step (l) for a range ofrefractory periods.
 9. The method according to claim 8, furthercomprising treating atrial fibrillation in the portion of the heart. 10.A method for treating atrial fibrillation in an atrium of a heart of apatient, comprising the steps of (a) acquiring an image or map of theatrium; (b) displaying the image or map of the atrium; (c) marking atleast one feature on the image or map; (d) calculating dimensions of theat least one feature; (e) identifying one or more points on or withinthe atrium for treatment as part of a treatment plan; (f) determiningpaths to the one or more points on or within the atrium for treatmentbased on the dimensions of the at least one marked feature; (g)simulating, on a computer, insertion of a sheath into the atrium throughone of the paths; (h) simulating, on the computer, insertion of amedical device through the sheath and into the atrium; (i) verifyingthat the one or more points on or within the atrium can be accessed bythe medical device for treatment as part of the treatment plan; (j)computing an overall surface area of the atrium; (k) calculating anestimated area not treated in the atrium based on the treatment plan andin accordance with the overall surface area of the portion of the heart;(l) assessing whether macro-reentrant circuits can exist in theestimated area not treated in the atrium; (m) repeating steps (e)—(l) inthe event step (l) indicates that macro-reentrant circuits can exist inthe estimated area not treated in the atrium; and (n) implementing thetreatment plan of steps (g) through (i).
 11. The method according toclaim 10, further comprising measuring an actual area not treated in theatrium after step (n).
 12. The method according to claim 11, furthercomprising assessing whether macro-reentrant circuits can exist in theactual area not treated in the atrium.
 13. The method according to claim12, further comprising repeating steps (e)-(l) in the event step (l)indicates that macro-reentrant circuits can exist in the actual area nottreated in the atrium.
 14. The method according to claim 13, furthercomprising implementing a revised treatment plan in the event step (l)indicates that macro-reentrant circuits can exist in the actual area nottreated in the atrium.
 15. The method according to claim 14, furthercomprising monitoring the treatment and robotically guiding the medicaldevice according to the treatment plan.
 16. The method according toclaim 14, further comprising using ablation as the treatment.
 17. Themethod according to claim 16, further comprising conducting step (l) fora range of refractory periods.